STAPHYLOCOCCI. INTRODUCTION Staphyloccocci - derived from Greek “stapyle” (bunch of grapes) Gram...
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Transcript of STAPHYLOCOCCI. INTRODUCTION Staphyloccocci - derived from Greek “stapyle” (bunch of grapes) Gram...
STAPHYLOCOCCI
INTRODUCTION
• Staphyloccocci - derived from Greek “stapyle” (bunch of grapes)
• Gram positive cocci arranged in clusters
• Hardy organisms surviving many non physiologic conditions
• Include a major human pathogen and skin commensals
Grouping for Clinical Purposes
• 1. Coagulase positive Staphylococci– Staphylococcus aureus
• 2. Coagulase negative Staphylococci– Staphylococcus epidermidis– Staphylococcus saprophyticus
A. Staphylococcus aureus
• Major human pathogen
• Habitat - part of normal flora in some humans and animals
• Source of organism - can be infected human host, carrier, fomite or environment
Natural history of disease
• Many neonates, children, adults -intermittently colonised by S. aureus
• Usual sites - skin, nasopharynx, perineum
• Breach in mucosal barriers - can enter underlying tissue
• Characteristic abscesses• Disease due to toxin production
DISEASES
• Due to direct effect of organism– Local lesions of
skin– Deep abscesses– Systemic
infections
• Toxin mediated– Food poisoning– toxic shock
syndrome– Scalded skin
syndrome
SKIN LESIONS• Boils• Styes• Furuncles(infection of hair follicle)• Carbancles (infection of several hair follicles)• Wound infections(progressive appearance of
swelling and pain in a surgical wound after about 2 days from the surgery)
• Impetigo(skin lesion with blisters that break and become covered with crusting exudate)
DEEP ABSCESSSES
• Can be single or multiple
• Breast abscess can occur in 1-3% of nursing mothers in puerperiem
• Can produce mild to severe disease
• Other sites - kidney, brain from septic foci in blood
Systemic Infections• 1. With obvious focus
– Osteomyelitis, septic arthritis
• 2. No obvious focus• heart (infective endocarditis)
• Brain(brain abscesses)
• 3. Ass. With predisposing factors – multiple abscesses, septicaemia(IV drug
users)– Staphylococcal pneumonia (Post viral)
B. TOXIN MEDIATED DISEASES
• 1. Staphylococcal food poisoning– Due to production of entero toxins– heat stable entero toxin acts on gut– produces severe vomiting following a very
short incubation period– Resolves on its own within about 24 hours
2. Toxic shock syndrome
• High fever, diarrhoea, shock and erythematous skin rash which desquamate
• Mediated via ‘toxic shock syndrome toxin’• 10% mortality rate• Described in two groups of patients
– ass. With young women using tampones during menstruation
– Described in young children and men
3. Scalded skin syndrome
• Disease of young children• Mediated through minor Staphylococcal
infection by ‘epidermolytic toxin’ producing strains
• Mild erythema and blistering of skin followed by shedding of sheets of epidermis
• Children are otherwise healthy and most eventually recover
DIAGNOSIS
• 1. In all pus forming lesions – Gram stain and culture of pus
• 2. In all systemic infections– Blood culture
• 3. In infections of other tissues– Culture of relevant tissue or exudate
2. Staphylococcus epidermidis
• Skin commensal• heart valves, • Causes urinary tract infection in
cathetarised patients
3. Stapylococcus saprophyticus
• Skin commensal
• Imp. Cause of UTI in sexually active young women
• Usually sensitive to wide range of antibiotics